Hi J.,
Your situation sounds tough.
My oldest son has "ADHD". He wasn't violent but he would change at the drop of a hat also. He is an extremely smart person and would, all of a sudden, be nearly retarded. I couldn't understand how he could change so suddenly. I would get so furious because I thought he was pretending and playing games with me.
Fortunately, for us, I was given a tape to watch. It talked about how 80% of the children diagnosed with ADHD actually have food allergies. As it turns out, my son was allergic to whole wheat. For some reason, his brain would be unable to function about 20 minutes after he ate whole wheat. I don't understand it, but it is true right to this very day.
According to the tape, whole wheat and dairy are a the two main foods that cause the problem. I decided to take my son off of those two to see what would happen. Then I would reintroduced the foods. He was completely normal without them for two whole weeks. I added back in the dairy and he was just fine for another week. The day I added back the whole wheat is the day he became "retarded" again. Then I realized that all of his problems started when I decided to improve our diet with whole grains.
Your son may be one of the 20% who actually has ADHD. However, I think the food elimination diet would be a good thing to try...maybe he is one of the 80%!
Best wishes,
T.